Rotationally stabilized projectiles are corrected in their path, from launcher to target, for example by the deployment and retraction of guide fins and/or brake flaps during travel of the projectile in its path. One problem is the high energy consumption which is incurred when the fins (brake and rotation fins or other fins) frequently need to be deployed and retracted during travel of the projectile from launcher to target.
The target precision for a projectile in an artillery system is largely controlled by meteorological aspects and how closely the actual launch velocity, V0, matches the calculated launch velocity, as well as by launcher-related factors, such as the configuration of the barrel and the exactness of the aiming system. Before guidable projectiles began to be used in artillery applications, there was no possibility of affecting the trajectory of the projectile after the projectile had left the barrel.
Through the introduction of guide mechanisms, such as rudders, flaps or fins/wings, the guidability of a projectile is able to be controlled. Depending on the configuration, placement and size of the fins/wings, various degrees of dirigibility can be obtained. Different dirigibilities are required, depending on the configuration, V0, firing range, altitude and target precision of the projectile. Reliable techniques have also been developed for calculating the current position of a projectile, based on inertial navigation and/or satellite navigation via a GNSS system, such as, for example, GPS. Projectiles are also constructed with a GNC system and the GNSS system can be said to be a part of the GNC system. GNC, which stands for Guidance, Navigation and Control, ensures that the projectile is guided towards the target for which the projectile is meant.
One specific guidance method for projectiles requires that fins, such as brake flaps and rotation fins, are frequently deployed and retracted from the projectile during travel of the projectile from launcher to target. With currently known design solutions, the energy consumption will be very high, especially when the fins are retracted from the deployed position, since a large, centrifugally created force must be overcome.
GB 2,121,147 A describes a fin deployment mechanism for a missile in which fins are mounted, with lever arms and pivot pins, against an inner part arranged in a rotatably concentric manner relative to the cylindrical missile. The device is spring-loaded and the fins are deployed after a locking mechanism releases the inner part, which, through a rotary motion, deploys the fins. No radial motion for deployment of the fins is described, nor retraction of the fins, or that the inner part is adapted to constitute a counterweight or to otherwise reduce the energy consumed in the deployment operation.
One problem with known constructions of fin deployment mechanisms is that the energy which is used to deploy and, above all, retract the fins is large.
Another problem with known constructions of fin deployment mechanisms is that a powerful motor or a powerful servo is needed to retract or deploy the fins. A powerful motor/servo consumes large quantities of energy and takes up a large amount of space in the projectile.
A further problem with the said projectile constructions is that energy sources in the form of batteries or other energy-storing methods are bulky, are prone to ageing, or are for other reasons unsuitable for integration on projectiles. There is therefore a desire to reduce the size of the energy sources or wholly avoid energy sources.
Further problems which the invention aims to solve emerge in connection with the following detailed description of the different embodiments.